PubMed Health⌕ Search

Biomedical subjects

R E Canfield

Publications and source records attributed to R E Canfield.

At least 37 records · Page 2Linked to original sources
PubMed1989

Parathyroid function in Paget's disease of bone.

In order to determine the prevalence of secondary hyperparathyroidism in patients with Paget's disease of bone, we measured serum parathyroid hormone levels (N-terminal assay) in 39 patients with a wide range of pagetic activity. All patients had normal serum calcium levels. A total of 30 patients were either untreated or had received no treatment for 6 months or longer when studied; the other 9 were receiving either salmon calcitonin (3) or EHDP (6). The results showed that in 7 of the 39 patients (18%) parathyroid hormone levels were increased above normal. These were among the most severely affected cases, as manifested by the degree of elevation of three pagetic biochemical indices: serum alkaline phosphatase, plasma bone Gla protein, and 24 h urinary hydroxyproline-creatinine ratios. Levels of 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 were normal. We examined the relationships between parathyroid hormone and each of the three pagetic indices as well as serum calcium for the entire group of 39 patients. Parathyroid hormone values did not correlate with serum calcium measurements (r = -0.241, p = NS) but did correlate significantly with serum alkaline phosphatase (r = 0.496, p less than 0.001), plasma bone Gla protein (r = 0.537, p less than 0.001), and urinary hydroxyproline (r = 0.450, p less than 0.011). We conclude that relative or absolute increases in parathyroid hormone may occur in moderately active Paget's disease, possibly in the setting of greater calcium demands during periods of increased pagetic new bone formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Early alpha chain crosslinking in human fibrin preparations.

Purified fibrinogen preparations were clotted under crosslinking conditions and the evolution of alpha polymers was examined by Western blotting (SDS-PAGE). Monoclonal antibodies that bind to two localized regions within the COOH-terminal portion of the (A) alpha chains of fibrinogen (F-103, A alpha #259-276; F-102, A alpha #540-554) were used for immunodetection. Three crosslinked components (100K, 168K, 210K) that each exhibited coincident F-102 and F-103 immunoreactivities were evident as early as gamma dimer formation under the in vitro conditions employed. Initial events in the alpha chain crosslinking process appeared to include interactions between relatively intact chains and a variety of degraded ones that shared the structure A alpha #1-276, but differed in the extent to which regions between residues approximately #276 and approximately #539 were preserved. Degraded fibrinogen molecules whose A alpha chains all terminated before A alpha #540-554 were isolated from purified fibrinogen preparations by immunoaffinity chromatography on F-102 Sepharose. Immunoblotting data obtained for the crosslinking capacity of these degraded molecules indicated that early crosslinked components (95 K, 205 K) could form even in the absence of intact alpha chain partners. This crosslinking, moreover, could progress to the polymer stage. These findings demonstrate that some early crosslinking activity is localized exclusively within regions NH2-terminal to A alpha approximately #540-554 and suggest that fibrinogen molecules with partially degraded A alpha chains, which are likely to be circulating under many pathophysiologic conditions, can undergo fibrin stabilization through crosslinking despite a loss of at least 70 COOH-terminal A alpha chain residues.

Blotting, Western↗
PubMed1988

Immunochemical characterization of crosslinked derivatives isolated from alpha chain oligomers formed during early stages of fibrin crosslinking.

Early crosslinked alpha chain oligomers (E alpha XL) that formed within 1/2 h of in vitro clot formation were isolated from preparations of reduced, carboxymethylated fibrin by gel filtration on Sepharose CL-4B. Cyanogen bromide (CNBr) digestion of E alpha XL released a mixture of fragments which could be partially separated by Sephadex G-150 chromatography. Crosslinked and non-crosslinked forms of the A alpha chain peptides, CNBr VIII (A alpha #241-476) and CNBr X (A alpha #518-584) were identified in the column effluent both by radioimmunoassay (RIA) and by immunoblotting using polyclonal antisera (anti-CNBr VIII, anti-CNBr X) and monoclonal antibodies (F-103, binds to A alpha #259-276; F-102, binds to A alpha #540-554), respectively. Immunoaffinity chromatography of the crosslinked material, on F-103, followed by F-102 Sepharose, resulted in the separation of two types of fragments, each of which contained an early alpha chain crosslink. One of these (35-37K) exhibited coincident CNBr VIII and CNBr X immunoreactivities, while the other (54-59K) exhibited only CNBr VIII immunoreactivity, based on immunoblotting and RIA findings. NH2-terminal sequencing and cyanoethylation data provided biochemical evidence for the occurrence of covalent CNBr VIII-X as well as covalent CNBr VIII-VIII interactions during early alpha chain crosslinking. These findings indicate, for the first time, that both glutamine acceptor and lysine donor activities may be localized within CNBr VIII. This information should facilitate the chemical identification of alpha chain residues that partner during factor XIIIa-catalyzed cross-linking and thus enable development of reagents for the generation of fibrin-specific antibodies.

Amino Acids↗
PubMed1988

Incidence of early loss of pregnancy.

We studied the risk of early loss of pregnancy by collecting daily urine specimens from 221 healthy women who were attempting to conceive. Urinary concentrations of human chorionic gonadotropin (hCG) were measured for a total of 707 menstrual cycles with use of an immunoradiometric assay that is able to detect hCG levels as low as 0.01 ng per milliliter, with virtually 100 percent specificity for hCG in the presence of luteinizing hormone. Our criterion for early pregnancy--an hCG level above 0.025 ng per milliliter on three consecutive days--was determined after we compared the hCG levels in the study group with the levels in a comparable group of 28 women who had undergone sterilization by tubal ligation. We identified 198 pregnancies by an increase in the hCG level near the expected time of implantation. Of these, 22 percent ended before pregnancy was detected clinically. Most of these early pregnancy losses would not have been detectable by the less sensitive assays for hCG used in earlier studies. The total rate of pregnancy loss after implantation, including clinically recognized spontaneous abortions, was 31 percent. Most of the 40 women with unrecognized early pregnancy losses had normal fertility, since 95 percent of them subsequently became clinically pregnant within two years.

Abortion, Spontaneous↗
PubMed1988

Development of highly sensitive immunoassays to measure human chorionic gonadotropin, its beta-subunit, and beta core fragment in the urine: application to malignancies.

A variety of malignancies have been associated with the presence of human chorionic gonadotropin, hCG, its subunits, and fragments of its beta-subunit in blood and urine. The usefulness of these hCG-related tumor markers in nontrophoblastic malignancies has been inhibited by inadequate assay techniques. In order to achieve the required sensitivity and specificity, concentration steps and other procedures to remove cross-reacting human luteinizing hormone were necessary. In addition, the coexistence of a fragment of the hCG-beta or beta human luteinizing hormone subunit contributes to significant errors of measurement in urine. The importance of the hCG-beta fragment as a potential tumor marker has been recognized previously but no method was available to measure this antigen readily. We report here the development of a series of radioimmunometric, two-site assays which will accurately measure hCG, hCG-beta subunit, and the beta-subunit fragment directly in small volumes of unprocessed urine. These assays are highly specific, extremely sensitive, and not labor intensive since they employ microtiter plate procedures. Application of these assays to urine samples from patients with gynecological malignancies indicated that over 50% of all patients tested excreted the hCG-beta fragment in their urine. Also, this fragment comprised more than 50% of the moles of hCG immunoreactive components present in the specimens that were positive for hCG. This cancer marker is also demonstrable in trophoblastic malignant states such as choriocarcinoma in which the low molecular weight fragment can also be visualized directly by immunoblotting procedures. We conclude that a search for hCG immunoreactivity in the urine of patients with malignancies will be improved by the inclusion of accurate measurements of the prominent quantities of the beta fragment excreted by these individuals.

Biomarkers, Tumor↗
PubMed1988

Measuring human chorionic gonadotropin for detection of early pregnancy loss.

Elucidation of the primary molecular structure of hCG, coupled with monoclonal antibody technology, has permitted the construction of a partial map of hCG surfaces. Based on this information, two-site immunoradiometric assays have been developed which permit the measurement of intact hCG and its subunit molecular forms with unprecedented sensitivity and specificity. These assays have been employed in a determination of the incidence of early pregnancy loss in a normal population with the finding that 22% of all conceptions producing measurable hCG terminate before becoming clinically evident.

Abortion, Spontaneous↗
PubMed1988

Heterogeneity of proteins in commercial preparations of human chorionic gonadotropin (hCG) demonstrated by Western blotting.

Immunoblotting has been utilized to detect the presence of human chorionic gonadotropin (hCG), its alpha and beta subunits, the Tamm-Horsfall protein (uromodulin), immunoglobulins G (IgG) and M (IgM), kappa (K) and lambda (L) chains, and serum albumin in commercially available preparations of hCG intended for human use. Concentrated pregnancy, postpartum, and normal urines were studied as a comparison. Those hCG batches prepared from pooled first-trimester pregnancy urine contained all of the hCG and non-hCG proteins listed above or their fragments, with the single exception of the IgM mu chain. The conflicting literature regarding the immunomodulatory properties of hCG requires reevaluation, since many previous reports of immunologic activity utilized these preparations, containing intact and degraded IgG, K, and L chains, and the Tamm-Horsfall protein, all of which may contribute to an altered immune response. Since hCG can be prepared in high yields, free of these contaminants, these data suggest that patients are being unnecessarily exposed to contaminating substances when receiving parenteral injections of hCG.

Antibodies, Monoclonal↗
PubMed1988

Structure of the human chorionic gonadotropin beta-subunit fragment from pregnancy urine.

A major portion of the hCG immunoreactivity detectable in pregnancy urine is derived from a fragment of hCG beta. This lacks the COOH-terminal portion of hCG beta, but retains immunoreactivity with most antibodies raised against the beta-subunit of hCG. To improve clinical measurements of hCG and assess the importance of such fragments in human urine, we have isolated and determined the structure of this molecule. The hCG beta fragment was isolated from a partially purified commercial preparation of hCG (Organon) by gel filtration and immunoaffinity chromatography using monoclonal antibodies. It was found to consist of two polypeptide chains composed of residues beta-(6-40) disulfide-bridged to residues beta-(55-92). It also differs from the beta-subunit of hCG in its carbohydrate structure, lacking sialic acid and having a low but variable amount of galactose. A beta-fragment containing the same two NH2-terminal sequences was also isolated from a single pregnant woman's urine. The two major polypeptides comprising the beta-fragment contain a total of nine half-cystine residues, raising the possibility that a free thiol may exist or that a third undetected disulfide-bridged peptide is present in the intact fragment. However, tests for the presence of a free thiol have been negative. Another intrinsic characteristic of the beta-fragment is the formation of a variable amount of dimer in solutions of neutral pH. beta-fragment will not combine with intact alpha-subunit. Despite the absence of regions beta-(1-5), beta-(41-54), and beta-(93-145), the beta fragment is recognized by the SB-6 antibody and most monoclonal antibodies elicited to the beta-subunit, thus excluding half of the amino acids of the beta-subunit from the epitope(s) where these antibodies bind.

Amino Acid Sequence↗
PubMed1988

Preparation and characterization of antibodies to the urinary fragment of the human chorionic gonadotropin beta-subunit.

hCG is a glycoprotein hormone composed of two dissimilar subunits (alpha and beta) and is normally synthesized by trophoblastic tissue. Its measurement by immunoassay is widely employed as a test for pregnancy, but can be complicated by cross-reactivity with human (h) LH. Immunoassays based on the beta-subunit of hCG have been employed to decrease this cross-reactivity with hLH, but when these assays are used with urine specimens, the antibodies employed also detect a fragment of hCG beta, which can lead to significant differences in measurement. To overcome these problems, we have developed a series of monoclonal antibodies to the beta fragment of hCG recovered from pregnancy urine. Some of the antibodies that bind to this beta fragment are directed to a region of hCG beta that is different from the epitopes recognized by antibodies raised against the intact beta-subunit. The new epitopes available in the hCG beta fragment form the basis for novel immunoassays. These beta fragment antibodies are used in conjunction with other antibodies, directed to different epitopes of the hormone, to produce a series of immunoradiometric assays that can discriminate among intact hormone, free hCG beta, and hCG beta fragment. The hCG beta fragment antibodies described herein have affinities between 10(9) and 10(11) M-1 for the beta fragment and exhibit varying degrees of discrimination between the hCG beta fragment, the beta-subunits of hCG and hLH, and intact hCG and hLH.

Animals↗
PubMed1987

Detection of desialylated forms of human chorionic gonadotropin.

Urinary forms of human chorionic gonadotropin (hCG) with oligosaccharides deficient in sialic acid content (ashCG) have been reported to be excreted by patients with choriocarcinoma in greater amounts than by healthy, pregnant women. Although ashCG potentially could be a useful marker for the diagnosis and management of gestational trophoblastic neoplasia, the methods previously used for its detection were not suitable for routine clinical application. Therefore, we have devised a simpler method which can provide specific and sensitive measurements of ashCG in urine. This method, which is designated as a lectin-immunoradiometric assay (LIRMA), employs an agarose-coupled lectin to selectively extract the ashCG, which is then quantified directly with a purified and radiolabelled rabbit antibody. The LIRMA has been applied to demonstrate that there is an increased excretion of ashCG by choriocarcinoma patients. It is also applicable, in principle, for the study of any glycoprotein which has a reduced content of sialic acid in its carbohydrate side chains.

Chorionic Gonadotropin↗
PubMed1987

Development of an assay for a biomarker of pregnancy and early fetal loss.

Human chorionic gonadotropin (hCG) is a glycoprotein hormone, secreted by the syncytiotrophoblast cells of the fertilized ovum, that enters the maternal circulation at the time of endometrial implantation. It is composed of two nonidentical subunits; alpha and beta, with molecular weights of 14 kD and 23 kD, respectively. Its alpha subunit is identical in primary structure to its glycoprotein homologs, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH). Human chorionic gonadotropin binds to the same receptor as hLH and displays the same biological response, namely, to stimulate the declining function of the corpus luteum to produce progestins and estrogen late in the menstrual cycle. The differences in the structures of hCG and hLH have been exploited to develop antibodies that can measure hCG specifically in the presence of hLH. Two-site antibody binding assays have been developed, based on a surface immunological concept of hCG epitopes, that involve four distinct regions to which antibodies against hCG can bind simultaneously. Antibody cooperative effects, in conjunction with kinetic advantages derived from the concentration factors by use of the sandwich assay technique (immunoradiometric assay, IRMA), have enabled development of extremely sensitive and specific measurement protocols for urinary hCG. The assay described herein permits the detection of pregnancy on an average 25.4 days after the first day of the preceding menses, as opposed to 29.5 days for conventional radioimmunoassay techniques. In addition, the greater sensitivity and specificity of this assay method has permitted the detection of episodes of fetal loss not detected by radioimmunoassay of urine specimens. A large scale epidemiological study is in progress using this assay technique as a way to identify pregnancies that are lost before becoming clinically apparent. This methodology provides a valuable tool for the determination of the rate of early fetal loss.

Amino Acid Sequence↗
PubMed1987

The use of biochemical assays in epidemiologic studies of reproduction.

Recent progress in the assay of urinary hormones has opened new opportunities for epidemiologists to study hormones and health outcomes. This is especially true for studies of female reproduction. The cyclic nature of female reproduction can be fully described only by continuous frequent measurements that, in order to be practical, require easily collected biological specimens. We describe our experience in collecting and analyzing daily urine specimens from 301 healthy women. We conclude that this approach is not only feasible but potentially of great value to epidemiologists for studying fertility, early pregnancy, the effects of toxic exposures on reproduction, and the relationships between reproduction and later risk of chronic diseases.

Adult↗
PubMed1987

Dichloromethylene diphosphonate action in hematologic and other malignancies.

We have studied the administration of both oral and intravenous dichloromethylene diphosphonate (Cl2MDP) in patients with hypercalcemia and/or hypercalciuria due to increased bone resorption in the setting of multiple myeloma (N = 16) or chronic lymphocytic leukemia (N = 1). The effectiveness of 1600 mg of oral Cl2MDP twice daily was studied in 14 subjects with refractory multiple myeloma, active osteolytic disease and either persistent hypercalciuria (urinary Ca greater than 200 mg per g creatine on a low Ca intake) or hypercalcemia (serum Ca greater than 11.0 mg/dl), in a double-blind, placebo-controlled, 16 week-long trial. Of the 12 patients who received Cl2MDP (2 died in the placebo phase), 11 had marked reductions in urinary calcium (P less than 0.001), which fell into the normal range in 9. Urinary hydroxyproline decreased significantly in 8. Eight of the 11 responders also appeared to have decreases in bone pain associated with Cl2MDP therapy. Similar results were found when this protocol was used in a study of 10 women with breast cancer metastatic to bone. In addition, intravenous Cl2MDP was studied in 12 patients with hypercalcemia of malignancy, of whom 2 had multiple myeloma and 1 had chronic lymphocytic leukemia (CLL) associated with extensive osteolytic bone destruction. We gave 2.5 mg/kg on the first treatment day and 5 mg/kg daily thereafter for up to six more days. Serum calcium fell to normal after a mean of four days in the three patients with hematologic malignancies as well as in eight of the nine with solid tumors. Both urinary Ca and OHP also declined significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1987

Urinary human chorionic gonadotropin among intrauterine device users: detection with a highly specific and sensitive assay.

The mechanism by which the intrauterine device (IUD) prevents clinical pregnancy has not been established. The possibility that the IUD works primarily at the time of implantation or beyond has raised legal and ethical concerns. Numerous studies have measured human chorionic gonadotropin (hCG) among IUD users as a way to determine whether implantation routinely occurs in the presence of an IUD. Both positive and negative findings have been reported, reflecting major difficulties in the measurement of hCG at low levels. In this study, we collected daily urine specimens for up to three menstrual cycles from 40 women who used nonmedicated IUDs. We assayed these urines with an immunoradiometric assay that is highly specific for hCG at very low concentrations. This assay allows us to describe patterns of hCG rise and fall that would be undetectable by standard radioimmunoassays. In this study of IUD users, we found only one incident of probable early pregnancy loss among 107 cycles. With the use of an assay sensitive to hCG at levels as low as physiologic background, the possibility of frequent unrecognized implantation among IUD users can be reasonably excluded.

Adult↗
PubMed1986

Development of a radioimmunoassay for the fibrinogen-derived peptide B beta 1-42.

The peptide B beta 1-42 is the initial cleavage product of plasmin-mediated proteolysis of the NH2-terminal region of fibrinogen or fibrin I, while beta 15-42 is the major fragment released by plasmin degradation of fibrin II. Numerous studies have described the measurement of plasma B beta 1-42 levels as an index of plasmin activity. Previous assays were indirect and included quantitation of thrombin-increasable fibrinopeptide B immunoreactivity (TIFPB) or measurement of beta 15-42 with an antiserum (132) which cross-reacted with B beta 1-42. We report on a new antiserum (R142) directed against B beta 1-42 which does not cross-react with beta 15-42 or fibrinopeptide B. Employing this antiserum, a specific assay for B beta 1-42 was developed. This assay was used to measure plasmin-mediated B beta 1-42 release from fibrinogen and its subsequent proteolysis by thrombin. The selectivity constant (Kcat/Km) for thrombin cleavage of the B beta 14-15 bond of B beta 1-42 was 10(5)-fold less than that for proteolysis of the same bond in the intact fibrinogen molecule, thus explaining the stability of this peptide in the presence of thrombin activity in the blood. Similarly, the selectivity constant for plasmin cleavage of the B beta 21-22 bond of B beta 1-42 was 140-fold less than that for proteolysis of the B beta 42-43 bond of fibrinogen, indicating that secondary plasmin attack of the B beta 1-42 molecule is not physiologically important. The specific B beta 1-42 assay provided excellent recovery of peptide added to blood or plasma. Comparison of B beta 1-42 levels with TIFPB values in 37 patient samples yielded good correlation over a wide range of levels (r2 = 0.91). The median plasma B beta 1-42 level in 15 normal individuals was 1.2 pmol/mL. This is similar to the previously reported normal range for TIFPB (1 to 4 pmol/mL) but is higher than the normal level of 0.4 pmol/mL reported with the assay employing antiserum 132. This discrepancy reflects rapid removal of Arg (B beta 42) by plasma carboxypeptidase activity resulting in 50% loss of B beta 1-42 immunoreactivity with antiserum 132 but no loss with R142. To circumvent this problem, we have developed a beta 15-42 antiserum (R154) which, like antiserum 132, cross-reacts with B beta 1-42. However, B beta 1-42/beta 15-42 immunoreactivity with R154 is stable in the presence of carboxypeptidase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug Stability↗
PubMed1985

Characterization and relative orientation of epitopes for monoclonal antibodies and antisera to human chorionic gonadotropin.

We analyzed ten monoclonal antibodies and three polyclonal antisera directed against human chorionic gonadotropin by immunoassay in order to determine which pairs of antibodies are capable of binding simultaneously to hCG. A relative orientation of epitopes on the surface of hCG could be inferred from a matrix of data describing the abilities of particular antibody pairs to inhibit competitively or enhance the binding of each other. These results indicated that the binding site of each of the antibodies could be assigned to one of three different regions of the hCG molecule, and at least one antibody binding within each region exhibited a substantial preference for hCG relative to human luteinizing hormone. One of these regions is the COOH-terminal portion of the hCG beta subunit. A second region contains the binding site for the SB6 rabbit antiserum (which has been widely employed in clinical studies) as well as the binding sites of several monoclonal antibodies. Antibodies to this second region characteristically bind both the whole hormone and the free beta subunit. A third region contains the binding sites of a previously reported human antiserum and also several monoclonal antibodies. These antibodies characteristically react preferentially with the intact hormone relative to the free subunits. The information contained in the type of epitope map described here can be used as the rational basis for the design of two-site immunoradiometric assays for hCG and/or its subunits.

Animals↗